Topic

# Impeller

About: Impeller is a(n) research topic. Over the lifetime, 45119 publication(s) have been published within this topic receiving 242579 citation(s). The topic is also known as: Impeller, impellar & blades.

##### Papers

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Abstract: It is recognized that a detailed knowledge of turbulence parameters, as well as velocities, can aid in understanding and modelling mixing rate dominated phenomena in stirred vessels. Turbulent-flow parameters were measured in a baffled, Rushton turbine agitated vessel with a laser-Doppler velocimeter. The necessary corrections for the periodic, nondissipative velocity fluctuations in the near impeller region were made by an autocorrelation method. Two components of periodic fluctuation, one corresponding to impeller blade frequency, the other corresponding to twice that frequency, were found to be significant. With the periodicity removed, meaningful turbulence intensities, autocorrelation functions, turbulence scales, energy spectra, and turbulence energy dissipation reates were obtained. Integral scales and turbulence energy dissipation rates were a particular objective in this work because of their usefulness in modelling local mixing rates in turbulence flows. From an energy balance around the impeller and impeller stream, it was found that 60% of the energy transmitted into the tank via impeller was dissipated in that region, and 40% was dissipated in the bulk of the tank. An equation for calculating local energy dissipation rates from resultant fluctuation velocities and resultant turbulence macroscales, , appeared adequate. Constant A was found to be 0.85.

439 citations

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Abstract: Large eddy simulations were performed on the flow in a baffled stirred tank, drien by a Rushton turbine at Res 29,000. The simulation procedure consisted of a lattice ) Boltzmann scheme for discretizing the Naier ) Stokes equations, and a force- field technique for representing the action of the impeller on the fluid. The subgrid-scale model was a conentional Smagorinsky model with a Smagorinsky constant c s 0.12. s The uniform, cubic computational grid had a size of about 6 = 10 6 nodes. The com- puter code was implemented on a parallel, shared-memory computer platform. The results on the phase-resoled aerage flow, as well as on the turbulence characteristics, are compared with phase-resoled experimental data. The trailingortex structure in the ¤icinity of the impeller was well represented by the simulations.

309 citations

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01 Jan 1990-

Abstract: Part 1: Outline of the book history and applications the centrifugal compressor the radial turbine non-dimensional parameters for performance assessment and design selection. Part 2 Fundamental fluid mechanics and thermodynamics: the basic equations the dynamics of compressible, perfect gas flow definitions of efficiency loss coefficient definitions stator performance parameters. Part 3 Preliminary design and analysis of centrifugal compressors: non-dimensional parameters for design selection application of basic thermo-fluid dynamics to compressors impeller design diffuser performance, design and analysis. Part 4 Preliminary design and analysis of radial turbines: basic design concepts preliminary design of the rotor performance correlations rotor passage preliminary design of the stator exhaust diffuser. Part 5 Generalised computer based one-dimensional performance prediction: generalised gas dynamic analysis empirical flow models and loss correlations summary of prediction procedure. Part 6 Modelling of compressor impellers with separated flow: performance prediction models application to experimentation. Part 7 Geometric description of turbomachine blades and passages: surface definition by two-dimensional projection functional representation of two-dimensional curves geometry definition by three-dimensional surfaces functional representation of three-dimensional surfaces. Part 8 Computation of internal flows: categorisation of methods calculation domains inviscid solution methods viscous solution methods coupled viscous-inviscid methods modelling of stator flows. Part 9 Special problems associated with turbomachine design and operation: compressor surge and techniques to suppress it high pressure ratio compressors pulse operation of radial turbines variable geometry stator for radial turbines special features of radial turbine rotors turbine rotor cooling size effects and scaling. Appendices: preliminary design of centrifugal compressor impellers - computer program listing, description of the computer program preliminary design of radial turbine rotors - computer program listing, description of the program a summary of the governing equations for three-dimensional fluid flow - the conservation of mass, or continuity, equation, the momentum equation, the energy equation discretisation methods - finite difference, finite element, finite volume.

280 citations

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Abstract: Impeller effectiveness has often been evaluated via either mixing time, θm, or flow number, Fl; and a direct connection between the two has also been assumed in some cases Here, these concepts are considered in the light of recent theoretical and experimental work It is shown that an equation for mixing time recently published by BHR Group can be related to a basic turbulence model It is also shown that this equation is superior to those based on a theory linking mixing time to the flow generated by the impeller The new equation and theory implies that all impeller types of equal impeller-to-tank diameter ratio are equally energy efficient in achieving overall homogenisation On the other hand, impeller efficiency based on the flow generated, as measured by laser Doppler anemometry at equal measured power, suggests a significant difference between impeller types

270 citations

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Abstract: Numerical simulations of the flow field in baffled mixing tanks, based on three alternative methods, are presented and discussed. In the first method, the impeller is not explicitly simulated, and its effects are modelled by imposing suitable, empirically derived, boundary conditions to the external flow. In the second method, the whole vessel volume is divided into two concentric, partially overlapping, regions. In the inner region, containing the impeller, the flow field is simulated in the rotating reference frame of the latter, while in the outer region simulations are conducted in the reference frame of the laboratory. Information is iteratively exchanged between the two regions after azimuthally averaging and transforming for the relative motion. In the third method, the tank volume is divided into two concentric blocks, the inner one rotating with the impeller and the outer one stationary. The two blocks do not overlap and are coupled by a sliding-mesh technique. Predictions are presented here for baffled tanks stirred either by single and dual Rushton turbines (radial impellers) or by a constant-pitch helical impeller (axial impeller), and are compared with experimental data from the literature. Satisfactory results can be obtained by the first method only if reliable empirical data are available for the flow near the impeller, while large errors may arise if this is not known with reasonable accuracy. The other two methods both yield satisfactory results while requiring no empirical information, and thus allow a much greater generality.

266 citations